Add losetup. (Who knows, it might even work.)

1 files changed, 190 insertions, 0 deletions

diff --git a/toys/other/losetup.c b/toys/other/losetup.c
new file mode 100644
index 00000000..aa62222c
--- /dev/null
+++ b/toys/other/losetup.c
@@ -0,0 +1,190 @@
+/* losetup.c - Loopback setup
+ *
+ * Copyright 2012 Rob Landley <rob@landley.net>
+ *
+ * No standard. (Sigh.)
+
+USE_LOSETUP(NEWTOY(losetup, ">2S(sizelimit)#s(show)ro#j:fdca[!afj]", TOYFLAG_SBIN))
+
+config LOSETUP
+  bool "losetup"
+  default y
+  help
+    usage: losetup [-cdrs] [-o OFFSET] [-S SIZE] {-d DEVICE...|-j FILE|-af|{DEVICE FILE}}
+
+    Associate a loopback device with a file, or show current file (if any)
+    associated with a loop device.
+
+    Instead of a device:
+    -a	Iterate through all loopback devices
+    -f	Find first unused loop device (may create one)
+    -j	Iterate through all loopback devices associated with FILE
+
+    existing:
+    -c	Check capacity (file size changed)
+    -d	Detach loopback device
+
+    new:
+    -s	Show device name (alias --show)
+    -o	Start assocation at OFFSET into FILE
+    -r	Read only
+    -S	Limit SIZE of loopback association (alias --sizelimit)
+*/
+
+#define FOR_losetup
+#include "toys.h"
+#include <linux/loop.h>
+
+GLOBALS(
+  char *jfile;
+  long offset;
+  long size;
+
+  int openflags;
+  dev_t jdev;
+  ino_t jino;
+)
+
+/*
+todo: basic /dev file association
+  associate DEV FILE
+  #-a
+  cdfjosS
+  allocate new loop device:
+    /dev/loop-control
+    https://lkml.org/lkml/2011/7/26/148
+*/
+
+// -f: *device is NULL
+
+// Perform requested operation on one device. Returns 1 if handled, 0 if error
+static void loopback_setup(char *device, char *file)
+{
+  struct loop_info64 *loop = (void *)(toybuf+32);
+  int rc = 0, lfd = -1, ffd;
+  unsigned flags = toys.optflags;
+
+  // Open file (ffd) and loop device (lfd)
+
+  if (file) ffd = xopen(file, TT.openflags);
+  if (!device) {
+    int i, cfd = open("/dev/loop-control", O_RDWR);
+
+    // We assume /dev is devtmpfs so device creation has no lag. Otherwise
+    // just preallocate loop devices and stay within them.
+
+    // mount -o loop depends on found device being at the start of toybuf.
+    if (cfd != -1) {
+      if (0 <= (i = ioctl(cfd, LOOP_CTL_GET_FREE)))
+        sprintf(device = toybuf, "/dev/loop%d", i);
+      close(cfd);
+    }
+  }
+
+  if (device) lfd = open(device, TT.openflags);
+
+  // Stat the loop device to see if there's a current association.
+  memset(loop, 0, sizeof(struct loop_info64));
+  if (-1 == lfd || ioctl(lfd, LOOP_GET_STATUS64, loop)) {
+    if (errno == ENXIO && (flags & (FLAG_a|FLAG_j))) return;
+    if (errno != ENXIO || !file) {
+      perror_msg("%s", device ? device : "-f");
+      rc = 1;
+      goto done;
+    }
+  }
+
+  // Skip -j filtered devices
+  if (TT.jfile && (loop->lo_device != TT.jdev || loop->lo_inode != TT.jino))
+    goto done;
+
+  // Check size of file or delete existing association
+  if (flags & (FLAG_c|FLAG_d)) {
+    if (ioctl(lfd, (flags & FLAG_c) ? LOOP_SET_CAPACITY : LOOP_CLR_FD, 0)) {
+      perror_msg("%s", device);
+      rc = 1;
+      goto done;
+    }
+  // Associate file with this device?
+  } else if (file) {
+    char *s = xrealpath(file);
+
+    if (ioctl(lfd, LOOP_SET_FD, ffd)) perror_exit("%s=%s", device, file);
+    loop->lo_offset = TT.offset;
+    loop->lo_sizelimit = TT.size;
+    strncpy((char *)loop->lo_file_name, s, LO_NAME_SIZE);
+    s[LO_NAME_SIZE-1] = 0;
+    if (ioctl(lfd, LOOP_SET_STATUS64, loop)) perror_exit("%s=%s", device, file);
+    if (flags & FLAG_s) printf("%s", device);
+    free(s);
+  } else if (flags & FLAG_f) printf("%s", device);
+  else {
+    xprintf("%s: [%04llx]:%llu (%s)", device, loop->lo_device, loop->lo_inode,
+      loop->lo_file_name);
+    if (loop->lo_offset) xprintf(", offset %llu", loop->lo_offset);
+    if (loop->lo_sizelimit) xprintf(", sizelimit %llu", loop->lo_sizelimit);
+    xputc('\n');
+  }
+
+done:
+  if (file) close(ffd);
+  if (lfd != -1) close(lfd);
+  toys.exitval |= rc;
+}
+
+// Perform an action on all currently existing loop devices
+static int dash_a(struct dirtree *node)
+{
+  char *s = node->name;
+
+  // Initial /dev node needs to recurse down one level, then only loop[0-9]*
+  if (*s == '/') return DIRTREE_RECURSE;
+  if (strncmp(s, "loop", 4) || !isdigit(s[4])) return 0;
+
+  s = dirtree_path(node, 0);
+  loopback_setup(s, 0);
+  free(s);
+
+  return 0;
+}
+
+void losetup_main(void)
+{
+  char **s;
+
+  TT.openflags = (toys.optflags & FLAG_r) ? O_RDONLY : O_RDWR;
+
+  if (TT.jfile) {
+    struct stat st;
+
+    xstat(TT.jfile, &st);
+    TT.jdev = st.st_dev;
+    TT.jino = st.st_ino;
+  }
+
+  // With just device, display current association
+  // -a, -f substitute for device
+  // -j substitute for device
+
+  // new association: S size o offset rs - need a file
+  // existing association: cd
+
+  // -f(dc FILE)
+
+  if (toys.optflags & FLAG_f) {
+    if (toys.optc > 1) perror_exit("max 1 arg");
+    loopback_setup(NULL, *toys.optargs);
+  } else if (toys.optflags & (FLAG_a|FLAG_j)) {
+    if (toys.optc) error_exit("bad args");
+    dirtree_read("/dev", dash_a);
+  // Do we need one DEVICE argument?
+  } else {
+    char *file = (toys.optflags & (FLAG_d|FLAG_c)) ? NULL : toys.optargs[1];
+
+    if (!toys.optc || (file && toys.optc>1)) {
+      if (CFG_HELP) toys.exithelp++;
+      perror_exit("needs 1 arg");
+    }
+    for (s = toys.optargs; *s; s++) loopback_setup(*s, file);
+  }
+}